Solving the Mysteries of a Rising Sea

THE sea level is rising 2 millimeters a year, too little to notice year to year but enough to send the waves toward beach houses and sea walls over the next two generations.

The tidal marshes that once covered most of the Connecticut shoreline, having been replaced by train tracks, houses, Interstate 95, industry and marinas, were expected to get a new life from the creeping water. Scientists thought the remaining marshes would migrate inland. For some reason, many of them are not doing this.

To find out why, a graduate student at Connecticut College in New London is studying two adjacent marshes at Barn Island, a state wildlife refuge in Stonington, which are reacting differently. One is gradually accumulating more dirt and re-routing its grasses ever so slowly inland. The other is developing bare patches and growing more of the shorter grasses that usually stay right at the water’s edge.

”We have a lot of ideas, but no clear answers yet,” said Lenny Bellet, a 27-year-old candidate for a master’s degree in biology who also teaches marine science at Williams College at the Mystic Seaport Maritime Studies Program.

Connecticut Sea Grant, part of a Federal program based at the University of Connecticut at Avery Point, is putting up $29,000 to, among other things, measure the marshes’ elevations and sample their soil.

Mr. Bellet’s tedious and buggy work could later solve the mysteries resulting from a 6 to 7 centimeter rise in the water level since the last time marshes were sampled in the early 1970’s.

The sea has been rising all over the world for about 10,000 years, as the earth’s surface continues to react, slowly, to the melting glaciers from the end of the Ice Age. But the pace has quickened since the 1930’s.

Scientists who study the Eastern seaboard agree that marshes from Florida to Massachusetts are changing. At the current rate, the sea level will rise about 1.5 feet between now and the year 2100, many believe.

”Many areas will be flooded,” said said William Niering, a professor of botany at Connecticut College and one of Mr. Bellet’s advisers. Mr. Niering has been studying marshes for 25 years.

In many regions of the East Coast, dry land inland from marshy areas is destroyed as the waters creep inland. In others, the marshes themselves diminish.

In the marshes that aren’t adapting, such as the one at Barn Island, salt marsh hay won’t grow where there is more extensive flooding. In its place grows cord grass, a shorter variety that usually is found farther out from the high tide mark. The black rush, which normally forms a belt along the edge of the dry land, has moved inland, suggesting the marsh is migrating.

Jeffrey Donnelly, a doctoral candidate at Brown University, has documented that change in grasses in several places from Barn Island in Stonington to Cape Cod where, for unknown reasons, the marshes are adapting faster to sea-level rise than the Eastern Connecticut marshes.

Scientists aren’t sure of all the reasons for the accelerated sea rise. It’s fairly certain global warming plays a part in it, hastening the melting of the polar ice caps. Many scientists blame the industrial revolution and automobile pollution, which have poured extra carbon dioxide into the atmosphere for 150 years, for trapping heat on the planet.

So they watch the marshes, which are a barometer of the changes. Researchers can calculate sea-level changes going back thousands of years by digging deep into marshes and extracting thin cylinders of mud, which are just as readable as the rings in a tree trunk.

Tidal changes also can be measured by simply marking water levels on stable platforms attached to something relatively immovable, such as a pier or concrete geologic marker.

Working with Mr. Bellet on the marsh project are Kathryn Sobocinski, 22, a recent graduate in environmental studies at Connecticut College, and Alison Biddle, 20, a zoology major in the Class of 1999. The team marked out a grid in the soft swirls of Spartina patens, the region’s classic marsh grass that became rare years ago with the construction of houses and sea walls.

They used metal tape measures to set their area and then moved from point to point, using surveying equipment to calculate the marsh’s height, which is about 3 feet above sea level in most places.

Meanwhile, Mr. Bellet takes samples of the sediment. For his master’s project, he is trying to figure out whether sulfates in seawater are accumulating too quickly in some marshes, resulting in the bald patches and the inability to alter as the sea level rises.

The well-adapted marsh is known as the Wequetequock marsh. It is to the west of the boat launch. The marsh to the east is not adapting. It sits below a man-made pathway, which is far enough inland to be near bushes. Whether the man-made path contributes to the marsh’s problems isn’t certain.

Surveys at another marsh, the Cottrell, across from Wilcox Marine in Mystic, reveal that that marsh is not keeping up well with sea-level rise, either, Mr. Bellet said. The team is also surveying a privately owned marsh near Murphy Point in Mystic, a marsh on Mamicoke Island Natural Area on the Thames River (part of the Connecticut College Arboretum), and a marsh on the Pattagansett River in East Lyme.

He noted there is room at Barn Island for some of the marshes to move landward, unlike so much of the coast. ”That only happens when there is no development, no sea walls, no barriers, no fill. It needs a very gentle gradient.”

About This Article

Thirteen years ago, climate change’s effects on the United States coast had engaged scientists in Connecticut. This article, the first of a hundred I wrote for The New York Times’s regional and metro sections over a period of nine years, followed researchers into the marshes of southeastern Connecticut. When it comes to a rising sea, no one can doubt it. This article, based on reporting I did for The Day of New London, appeared in the Times’s Sunday Connecticut section. See this link.